Field
The disclosed embodiments generally relate to techniques for performing channel-sounding operations in wireless communication systems. More specifically, the disclosed embodiments relate to a collaborative channel-sounding process, which uses measurements taken during a first channel-sounding operation in a first frequency band to improve a second channel-sounding operation in a second frequency band.
Related Art
Channel sounding is commonly used technique for improving the performance of wireless communication systems, which operates for example by allowing a base station and an associated mobile unit to compensate for the impact of a wireless channel response. During the channel-sounding process, a communication channel is characterized by measuring the channel's response to various test signals. This measured response can then be used to perform equalization operations, and also to decide how to transmit data in parallel through multiple signal paths in multiple-input, multiple-output (MIMO) wireless systems.
In single-input, single-output (SISO) wireless systems, the channel-sounding process is a channel estimation process. However, in MIMO systems the channel-sounding process is more complicated because it involves identifying multiple signal paths between one or more antennas on the transmitter and one or more antennas on the receiver, which are used to facilitate parallel data transfers to achieve a maximum data rate. In practice, because of noise, interference and various systems impairments, it is not possible to measure the different signal paths precisely. Furthermore, the limited bandwidth provided by wireless systems makes it difficult to isolate links with similar delay profiles, which is commonly the case in indoor wireless environments. This is particularly true in line-of-sight (LOS) situations where a dominant path causes increase in measurement errors for other paths. As a consequence, MIMO systems typically converge to a beam-steering mode of operation which is less optimal for maximizing data rate.
Hence, what is needed is a technique for performing channel sounding in a MIMO system without the above-described problems.